A considerable number of new diagnostic tests have been developed recently for use in the clinical laboratory. These tests frequently require a number of pre-mixed reagents, applicators and diagnostic plates or slides. With the plethora of such tests, the number of pre-mixed reagents has also multiplied. Unfortunately, such reagent bottles for one test can become confused with the reagent bottles of one or more other tests. Heightening the difficulties is the fact that the reagent bottles are quite diminutive as it is frequently necessary to employ very small quantities of both to-be-analyzed sample and reagent. Moreover, if any of the components required for the diagnostic test are not readily at hand, delay in conducting the test will be caused. Consequently, a rack arrangement adapted for multiple uses to retain and visibly exhibit all of the means required for a specific test would indeed be useful.